The present invention relates to a system of a bottle made for instance from plastics material with a variable volume intended to contain a liquid, in particular a fizzy beverage or gasified or sparkling drink (referred to hereinafter as a fizzy drink) and of an associated co-operating device.
One often uses for containing an alimentary liquid a substantially cylindrical or polygonal bottle made from plastics material and having at its upper part a neck through which the liquid may be inserted into the bottle or poured outwards thereof.
In the case of sparkling or fizzy beverages, the bottles with a fixed volume do not permit to preserve their gas content in a satisfactory manner during the consumption thereof.
Indeed prior to the first use of the bottle, i.e. before its first being opened, the gas volume topping the contained liquid is reduced to a minimum in the zone inside of the neck and a pressure balance builds up between the gas dissolved in the liquid and the gas topping the latter. The initial gas content of the liquid is determined by this pressure equilibrium and may be predetermined in the case of a gasifying of the liquid.
At each successive use of the bottle, one portion of the contained liquid is poured to the outside and air enters the bottle to replace by an equal volume the liquid poured to the outside.
After every use, a new pressure balance is set up between the gas volume topping the liquid and the gas bubbles dissolved in the latter. The gas bubbles are migrating towards the surface of the liquid to balance the pressure inside of the bottle.
Therefore on each use, the air which enters the bottle decreases the partial pressure of the gas topping the liquid and thus causes a degasification of the latter.
This physical phenomenon is all the more important as the utilizations are spaced in time which generally occurs when the so-called "family" bottles are used, namely bottles with a volumetric capacity of 1.5 to 2 liters for instance.
This degasification constitutes a major inconvenience in the consumption of fizzy drinks since the decrease of the gas content of these beverages results in an impairment of their taste.
There is already known from the document U.S. Pat. No. 4,456,134 in the name of Cooper a vessel having a top opening for the filling and the pouring of fizzy drinks, which opening is extended towards the bottom of the vessel by a flexible and compressible or deformable middle wall. This document also proposes a device externally connecting the part above the bottom of the vessel to progressively adjust and maintain the internal volume thereof.
This external device at least partially and concentrically encloses the vessel or is eccentered with respect thereto so as to be easily adaptable to the different types of existing vessels and to be reusable fully or in part on another vessel after complete consumption of the liquid contained in the original vessel.
The solution proposed by Cooper has the inconvenience to require the user to always take with him the external device permitting to keep the bottle in a state of reduced volume, thereby significantly increasing the bulk of the bottle for example in the bag of the user without taking into account the fact that the user may easily forget to take this device with him.
Moreover after the initial filling of the bottles during the conditioning, the latter are stored for a more or less long period in warehouses or distribution centers where the consumer will later come to buy the desired drink.
For this storage period the bottles, Which always have some elasticity, are generally ending in becoming deformed or elongated under the effect of the strong internal pressure exerted by the gas dissolved in the liquid thereby resulting in the formation of an air space topping the liquid in the bottle, in which space the gas may escape and thus result in a previous degasification of the beverage before an external device may be used.
It is also possible during the conditioning of the bottle to take this elongation of the bottle during its storage into account by filling it with an amount of drink sufficient to occupy the initial volume or volume at rest of the bottle increased by the estimated elongation.
In this case however there will occur an outflow of the liquid out of the bottle upon its first being opened by the user through elastic relaxation of the bottle towards its state of initial volume, which is unacceptable.
There is also known another system aiming at coping with the degasification of the beverages during their consumption, which proposes to fit the bottle after its first being opened and after each subsequent use with a special closing stopper with a check valve and to provide a gas overpressure in the air volume topping the liquid to restore the initial pressure balance and to stop the escape of gaseous carbon dioxide within the bottle.
This known system however has the inconvenience of a high cost, a constraining utilization and above all this system surprisingly restricts but imperfectly the escape of the gas dissolved in the liquid.
Furthermore the increase of the air volume contained in the bottle during its use as well as a possible introduction of air under pressure may also be a drawback from the sanitary standpoint owing to the possible pollution of the liquid by the air entering the bottle.
The object of the present invention is therefore to remove the aforesaid inconveniences and to provide a system of a bottle with a variable volume and of an associated co-operating device permitting to fully avoid that the contained liquid goes flat or becomes staled since its initial conditioning until its total consumption and the manufacture of which should be inexpensive and its use should be simple.